Normal aircraft tracking

The new PhoDiR (Photonics-based fully digital radar) system is a working prototype for next-generation radars - designed to let pilots and air traffic control exchange far more information in a single signal.

Photonic systems promise:

Higher precision - less noise (interference) in the radar transmission

"We're still trying to find out exactly how much better it is than conventional radar. It's only a prototype - we don't have clear numbers yet."

The compact system could potentially be installed on aircraft, and has a very large bandwidth - allowing pilots to transmit detailed information directly to ground stations within range.

"In future, we imagine a system on an airplane that can scan objects around but also communicate what's happening in the cockpit - what has been said, movements in the airplane, everything," Dr Ghelfi told BBC News.

"One could imagine transmitting live streaming video, together with the radar surveillance data. The advantage would be that a single system can do the entire job, instead of multiple systems."

Experts say photonic radar can overcome some of the limitations of current electronic systems.

A laser produces a finely-tuned digital signature, which is converted into a radio frequency wave and transmitted from the radar antenna.

The returning wave is also converted via laser into a digital signal free from "jitter".

"Because the light is very precise, so is the radio frequency signal," said Prof David Stupples, an expert on radar systems at City University in London.

"Currently we produce the carrier wave using electronics. But then you've got to transport it up to the radar head through expensive, heavy cabling - and this creates noise in the system.

"But if you use light - with fibre optics - it is cheaper, lighter and crucially - it has less interference. It's very accurate."

Jason McKinney, of the US Naval Research Laboratory, said the performance of the system's transmitter and return signal converter were "world-class with respect to those of other photonics-based devices".

"These elements... are appealing components for future frequency-agile, software-defined radar architectures," he wrote in a commentary in Nature.

The main limitation on the system, he says, is range. It's not clear how a photonic ground radar could cover any greater swathe of ocean than current coastal stations.